A tire pressure monitoring system (TPMS), e.g., an electronic system designed to monitor an air pressure inside pneumatic tires on various types of vehicles, can support comfort and safety driving environment. Air pressure of each tire can be inspected for basic pre-driving inspection, and can improve tire durability, riding quality, braking power, fuel efficiency, and so on. If the air pressure of tire is dramatically beyond a recommended range, the tire may be worn fast and be damaged or destroyed finally. When the damage on the tire is severe, the air pressure inside a tire can cause a traffic accident. It is desired that a driver should check air pressure inside each tire before driving, but checking the air pressure inside each tire might not be easy. Thus, the TPMS included in a vehicle is widely used to give the driver a warning sign when at least one air pressure inside tires is beyond the recommended range.
The TPMS may include a sensor for automatically detecting an air pressure, a temperature, and the like inside each tire. Information collected by the sensor is provided to a driver via a head unit (e.g., a dashboard) so that the driver can check the air pressure inside the tires real-time. The warning sign provided by the TPMS reminds the driver, who doesn't pay attention on a status of tires, for tire checkup. Recently, it is required for vehicles being equipped with the TPMS in many countries.
The sensor included in the TPMS is capable of sensing air pressure and temperature inside the tires. Since the air pressure is proportional to the temperature according to the ideal gas law (i.e., PV=nRT, where P is pressure, V is volume, n is amount in moles, R is ideal gas constant, and T is temperature of the gas, respectively), the air pressure can vary with the temperature. Because temperature inside the tires can vary with operating environment such as season, ambient temperature, or the like, the air pressure inside the tires can be changed. Further, the air pressure inside the tires can be altered because the temperature inside tires can rise because of friction while the vehicle operates. It is important to provide the driver with information regarding the air pressure inside each tire, which varies continuously, may be valuable, but the driver can be distracted when a warning sign is frequently turned on or off in response to the changed air pressure inside the tires.